Elementary Technical Mathematics

Published by Brooks Cole
ISBN 10: 1285199197
ISBN 13: 978-1-28519-919-1

Chapter 9 - Section 9.2 - Solving Pairs of Linear Equations by Addition - Exercises - Page 332: 20


One common solution $\Rightarrow$ $(3,-3)$

Work Step by Step

We use the addition method below: We add the 2 equations: $12x+5y=21$ $13x+6y=21$ Multiply both sides of the 1st equation by $13$ and the 2nd equation by $-12$ to cancel $x$: $+156x+65y=+273$ $\underline{-156x-72y=-252}$ $-7y=21$ Solve for $y$: $y=\frac{21}{-7}=\frac{3}{-1}=-3$ Substitute into any of the 2 equations and solve for $x$: $12x+5y=21$ $12x+5(-3)=21$ $12x-15=21$ $12x=21+15$ $12x=36$ $x=\frac{36}{12}$ $x=3$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.